Homeostasis Flashcards
What is dynamic equilbrium
internal environment of the body fluctuating around a specific normal level
what are the 3 things homeostasis is important for
temperatrue
blood glucose
water
how is homeostasis important for temperature
conditions where it will cause enzyme to denature
ensures the maintenance of optimal conditions for enzyme action and cell function
an increase in body temperature above 40 °C would cause enzymes to denature
This is due to an increase in kinetic energy which would result in the breakage of hydrogen bonds holding the enzyme in a specific 3D shape
The active site will change shape and will no longer be complementary to the substrate molecule
An enzyme-substrate complex cannot form and the enzyme cannot catalyse that reaction anymore, leading to less efficient metabolic reactions
how is homeostasis important for blood glucose
Cells also need a constant supply of energy in the form of ATP to work efficiently
Glucose is respired to supply this ATP, meaning that the body needs to carefully monitor and control blood glucose concentrations
how is homeostasis important for water
crucial for the amount of water in the blood to remain constant
Water is lost during excretion of waste products, e.g. urine, and in sweat
The kidneys are responsible for regulating the amount of water in the blood
what is the control mechanism for maintaining body temperature
thermoregulation
how is vasodilation a cooling mechanism
Vasodilation of the blood vessels that supply skin capillaries, supplying the capillaries in the skin with a greater volume of blood, which then loses heat to the environment via radiation
what the cooling mechanisms
Vasodilation of the blood vessels
Sweating
Flattening of hairs
how is sweating a cooling mechanism
Sweat is secreted by sweat glands
This cools the skin by evaporation; heat energy from the body converts liquid water into water vapour
why is sweating less of an effective cooling mechanism during humid conditions
sweat evaporates more slowly due to a reduced concentration gradient between the sweat and the surrounding air
how is flattening of hair a cooling mechanism
The hair erector pili muscles in the skin relax, causing hairs to lie flat
These muscles can be described as effectors, as they respond to a change in body temperature
This stops them from forming an insulating layer of trapped air and allows air to circulate over skin; heat can therefore leave by radiation
what are warming examples
Vasoconstriction of blood vessels that supply skin capillaries
Boosting metabolic rate
Shivering
Erection of hairs
Less sweating
how is vasoconstriction of blood vessels a warming mechanism
During vasoconstriction the muscles in the arteriole walls contract, causing the arterioles near the skin to constrict and allowing less blood to flow through skin capillaries
Instead, the blood is diverted through shunt vessels, which are deeper in the skin and therefore do not lose heat to the environment
how is boosting metabolic rate a warming mechanism
Most of the metabolic reactions in the body are exothermic and this provides warmth to the body
In cold environments the hormone thyroxine, released from the thyroid gland, increases the basal metabolic rate (BMR), increasing heat production in the body
Adrenaline may also be released to speed up the metabolic rate and release more heat
how is shivering a warming mechanism
This is a reflex action in response to a decrease in core body temperature
This means it is a nervous mechanism, not a hormonal one
In this case muscles are the effectors and they contract in a rapid and regular manner
The metabolic reactions required to power this shivering generate sufficient heat to warm the blood and raise the core body temperature
How is the erection of hairs a warming mechanism
The hair erector pili muscles in the skin contract, causing hairs to stand on end
This forms an insulating layer over the skin’s surface by trapping air between the hairs and stops heat from being lost by radiation
how is less sweating a warming mechanism
The sweat glands will secrete less sweat when it is cold
This will reduce the amount of heat lost through the evaporation of sweat
role of the hypothalamus in thermoregulation
Mammals detect external temperatures via thermoreceptors found in the skin and mucous membranes
There are receptors for both heat and cold
These communicate with the hypothalamus along sensory neurones
The hypothalamus will send impulses along motor neurons to effectors to bring about a physiological response to changing external temperatures
does hypothalamus help regulate body temperature
Yes, by monitoring the temperature of the blood flowing through it and initiating homeostatic responses when it gets too high or too low
what is a negative feedback system
reversing a change in the body to bring it back within normal limits
If body temperature rises a negative feedback system will act to lower body temperature, bringing it back to normal
If blood glucose levels drop a negative feedback system will act to raise blood glucose, bringing it back to normal
describe a negative feedback control loop
A receptor detects a stimulus that is involved with a physiological factor
E.g. a change in temperature or blood glucose level
A coordination system transfers information between different parts of the body
- This could be the nervous system or the hormonal system
An effector carries out a response
Effectors are muscles or glands
what is positive feedback
the original stimulus produces a response that causes the factor to deviate even more from the normal range
how can hormones alter events inside a cell
by influencing gene expression
how do eukaryotes control gene expression
using transcription factors
